Platelet reactivity in paediatric cardiac surgery: Should pharmacological platelet protection be performed during cardiopulmonary bypass and deep hypothermic circulatory arrest in young infants?

  • Dr Andreas Straub, Dept. of Thoracic, Cardiac and Vascular Surgery, University Hospital of Tübingen, Germany
  • Prof Joseph Smolich, Australia and New Zealand Children's Heart Research Group, Murdoch Children's Research Institute, Melbourne, Australia
  • Dr Hans Peter Wendel, Dept. of Thoracic, Cardiac and Vascular Surgery, University Hospital of Tübingen, Germany
  • Prof Gerhard Ziemer, Germany
  • Prof Yves d'Udekem, Cardiac Surgical Unit, Royal Children's Hospital, Melbourne, Australia
  • Prof Christian Brizard, Cardiac Surgical Unit, Royal Children's Hospital, Melbourne, Australia
  • Prof Karlheinz Peter, Baker IDI Heart and Diabetes Institute, Melbourne, Australia
  • Dr Stephen Horton, Cardiac Surgical Unit, Royal Children's Hospital, Melbourne, Australia

    • Objective: Cardiopulmonary bypass (CPB) and hypothermia cause platelet activation and dysfunction, which can contribute to thrombotic events as well as bleeding during cardiac surgery. Short-acting platelet inhibitor administration can protect platelets against CPB- and hypothermia-induced damage. In young infants, however, platelets are immature and may therefore be hyporeactive during CPB. Hence, it is unclear whether pharmacological platelet protection may be beneficial in these patients. This study aimed to measure effects of CPB and hypothermia on platelets in young infants.
    Methods: Congenital cardiac defects were repaired in young infants using hypothermic CPB in centre 1 [n=15; median age: 9 (range: 1-622) days; lowest temperature: 26°C] and using deep hypothermic circulatory arrest (DHCA) in centre 2 [n=5, median age: 84 (range: 20-99) days; lowest temperature: 15°C).
    Using flow cytometry, the following platelet activation parameters were assessed before (baseline), during, and after CPB: percentages of platelet P-selectin expression and aggregate-bound platelets (all patients) and platelet GPIbα internalisation (centre 1).
    Results: In centre 1 the following significant (p<0.01) median changes of platelet parameters were observed: Compared to baseline platelet P-selectin expression and aggregation were increased 6-fold and 2.3-fold respectively directly after CPB. Compared to baseline GPIbα-expression was decreased 1.9-fold directly after CPB.
    In centre 2 P-selectin expression was increased 4-fold directly after DHCA compared to pre-DHCA values (p=0.031).
    Conclusion: In young infants distinct platelet activation occurs in both CPB with hypothermia and DHCA. Both patient groups may therefore benefit from pharmacological platelet protection.